The model is now close to being signed off by Hackenberg’s department, Hackenberg himself having undertaken a drive of more than 300 miles in the model last week to test its durability.

The XL1 is an innovative diesel-electric hybrid that’s claimed to be able to return more than 300mpg. Hackenberg said production was likely to be limited to 50 units to preserve its high-tech, early adopter appeal, but more could be built as engineering capacity for up to 5000 models was in place.

The model is now close to being signed off by Hackenberg’s department, Hackenberg himself having undertaken a drive of more than 300 miles in the model last week to test its durability.

Guys, do you read this stuff before you publish it? 300 miles to test durability? Makes you wonder why manufacturers bother to drive across deserts and Arctic tundra.... Why not just post a link to the original marketing press release if you're not going to add some editorial value.

If they're going to build this thing at all, and they've got the capacity in place to build 5,000 of them, they might as well just go the whole hog and build the 5,000. Building 50 of them to test the water is going to make the per-unit cost ridiculously high and limit any useful feedback from the real-world use of the car. Besides, over the entirety of VW's global marketplace 5,000 isn't much - they've sold 8 times that number of Golfs this year to date in the UK alone, so even if it's a loss project they'd still gain more than if they just make 50.